Fingerprint authentication apparatus

ABSTRACT

A fingerprint authentication apparatus has a combined visible/infrared light source, which illuminates a finger placed on an optical image sensor with both infrared light and visible light. The optical image sensor has a block with infrared sensitivity and a block within infrared sensitivity, and generates a fingerprint image from light scattered by the finger. The infrared sensitivity of the infrared-sensitive block of the optical image sensor is such that a clear image is obtained from a living organism, and an unclear image is obtained from a replica. If the finger is an actual living finger, the fingerprint images from both blocks are clear, but in the case of a replica, the image from the block having infrared sensitivity is clear, and the image from the block without having infrared sensitivity is unclear. A reference processing section compares the clarity of the fingerprint images from the block with infrared sensitivity and the block without having infrared sensitivity, and if there is a difference therebetween, judges that the finger was a replica. After this is done, an image processing section  14  extracts minutiae from the fingerprint image, and a comparison section compares the fingerprint data with fingerprint in a database.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an optical fingerprintauthentication apparatus.

[0003] 2. Related Art

[0004] Because one cost of today's widespread information systemincluding making use of computers is the risk of leakage of confidentialand private information and the danger of unauthorized access toconfidential areas, there is an urgent need in our information-intensivesociety for identification and authorization of individuals.

[0005] Approaches to this problem are, for example, the input of apersonal identification number (PIN) when using a cash card in anautomatic teller machine of a bank, and the mandatory reading of anauthorization card and input of a password when entering a computerroom. However, with cards being used for a broad spectrum of functions,the management of cards held by individuals has become troublesome.

[0006] Additionally, individuals forget their PINs or passwords, andthere is a danger that these will be leaked to or read by others.

[0007] The fingerprint has long been thought of as a good alternative toPINs and passwords as a means for individual authentication. Thefingerprint can be thought of as high-level identification information,and identification information which, of course, the individual is notrequired to memorize or recall.

[0008] In a general fingerprint comparison apparatus, when a fingerprintis input using an image sensor, a recognition section performs imageprocessing of the fingerprint, and detects characteristic points of thefingerprint, these being known as minutiae.

[0009] The similarity of the input fingerprint with a fingerprint in adatabase is calculated from the minutiae.

[0010] This similarity is represented by a value known as a score, thehigher being the score, the greater being the similarity of the inputfingerprint with a fingerprint in the database. If the score exceeds aprescribed threshold value, the input fingerprint is judged to be thesame as the fingerprint stored in the database.

[0011] In a fingerprint identification apparatus as described above,however, it is not possible to distinguish between the fingerprint of anactual living person and a replica thereof (that is, a copy of afingerprint created in a non-living medium).

[0012] For this reason, in a case in which it is possible to obtain aprecise photograph of a fingerprint of a living person, for example,there is a danger that if this were to be input in place of an actualliving fingerprint, the apparatus would erroneously recognize it as anactual living fingerprint.

[0013] In the past, various proposals have been made to avoid theabove-noted problem. For example, in Japanese patent No. 2554667,directed at an “individual authentication apparatus” (hereinafterreferred to as prior art example 1), the apparatus has means formeasuring the temperature at the location of the living body at whichthe authentication is to be done (specifically, a thermocouple disposedin the fingerprint reading section), means for judging whether or notthe measured temperature is within a pre-established body temperaturerange (30° C. to 38° C.), and means for performing a comparison forauthentication only in the case in which the result of the judgment wasthat the measured temperature was within the pre-established range.

[0014] According to this technology, it is possible to achieve anindividual authentication apparatus that does not recognize afingerprint taken, for example from a photograph or a cut-off finger,that is, from a location other than a part of the actual body of theperson to be authenticated.

[0015] Furthermore, this apparatus uses a contact-type method, in whicha finger is brought into contact with a fingerprint reading section andthe fingerprint is read.

[0016] In the Japanese unexamined patent publication (KOKAI)No.11-235452, directed at a “Lock opening apparatus with anidentification function” (hereinafter referred to as the prior artexample 2), there is language describing an optical fingerprintcomparison apparatus for use as a security measure for an amusementlocation.

[0017] This optical fingerprint comparison apparatus shines illuminationonto a fingerprint part of a finger brought into contact with a prism,the reflected light therefrom being guided to an image sensor, and thefingerprint pattern being detected therefrom.

[0018] This apparatus has means for making a fingerprint comparisonbetween priorly stored fingerprint data and the fingerprint patternpressed up against the prism, means for performing finger recognition,and a lock-opening means for opening a lock mechanism only when there isboth coincidence resulting from the comparison by the fingerprintcomparison means and finger identification by the finger identificationmeans.

[0019] The finger identification means can be body temperature, pulse,fingernails and skin, and the shape of the finger.

[0020] Additionally, in the Japanese unexamined patent publication(KOKAI) No.10-187954, directed at a “All-in-one fingerprint readingsystem with a heating resistor” (hereinafter referred to as prior artexample 3).

[0021] In contrast to the above-described contact-type system, in whichthe fingerprint reading means is separated from the means for measuringthe temperature of the body part, the system of the Japanese unexaminedpatent publication (KOKAI) No.10-18795 combines these two elements. Thatis, a fingerprint reading sensor, up against which the finger ispressed, has an active surface of an element that is highly responsiveto changes in temperature, and a built-in heating resistor for bringingabout a transient temperature change in the sensitive element.

[0022] The thermal change caused by the heating resistor results in anelectrical signal that differs, depending upon the thermal conductivitybetween the grooves and the raised portions of the lines of afingerprint in contact with the sensing element matrix.

[0023] Fingerprint recognition is performed based on the above, and itis possible to recognize whether or not the fingerprint is from part ofan actual living person during the fingerprint reading, via thecharacteristic heat released from a finger.

[0024] In the above-described prior art example 1, however, athermocouple is used to detect the temperature of the object undermeasurement, and because a judgment is made that the object is an actualperson if the temperature is within a prescribed temperature range (30°C. to 38° C.), if a fingerprint replica is raised to within theprescribed temperature, an erroneous judgment that the object is a humanbody will be made, thereby not solving the problem.

[0025] In the prior art example 2, a fingerprint pattern is recognizedby an image sensor 106 using a non-contact method, and a detector 101detects body temperature, pulse, or the like. In the case of bodytemperature detection, in the same manner as in the prior art example 1,it is possible to defeat this apparatus by simply warming up a replica.

[0026] In the case of pulse detection, the need to have quite asensitive sensor to measure the pulse makes this device impractical.Additionally, even if such as device were achieved, the auxiliarydetector (pulse detector) would become much more expensive than theimage sensor, which is the main sensor, this also making the deviceimpractical.

[0027] In the prior art example 3, the fingerprint reading section andthe body temperature detector are combined as one. However, because ofthe use of an element sensitive to changes in temperature as the sensorthat reads the fingerprint, this system is susceptible to changes inambient temperature, making it necessary, for example, to change thethreshold value between the summer and the winter, this presenting aproblem in terms of maintenance.

[0028] Accordingly, it is an object of the present invention to solvethe above-noted problems encountered the prior art, by providing stablefingerprint authentication, which is little influenced by the ambienttemperature.

[0029] Another object of the present invention is to provide afingerprint authentication apparatus that is maintenance free.

SUMMARY OF THE INVENTION

[0030] To achieve the above-noted objects, the present invention adoptsthe following described basic technical constitution.

[0031] Specifically, a first aspect of the present invention is afingerprint authentication apparatus having an imaging section, whichimages the object of fingerprint authentication using an optical imagesensor having sensitivity in the infrared region, an image processingsection, which performs image processing of data obtained from theimaging section, thereby obtaining a fingerprint image, and a comparisonsection, which performs a comparison of the thus-obtained fingerprintwith a priorly stored fingerprint image.

[0032] A second aspect of the present invention is a fingerprintauthentication apparatus having an imaging section which forms an imageof a fingerprint to be authenticated by an optical image sensor formedby a first optical image sensor having sensitivity in the infraredregion and a second optical image sensor having sensitivity in thevisible light region, first and second optical image sensors beingmutually neighboring, an image processing section, which processes thedata obtained from the image processing section and obtains afingerprint image therefrom, and a comparison section, which performs acomparison of the fingerprint image to be authenticated thus obtainedwith a priorly stored fingerprint.

[0033] More specifically, the optical image sensor of the presentinvention is a CCD or CMOS device, and in the optical image sensor orblock with infrared sensitivity used in the present invention a deepP-well structure is formed directly beneath an N channel, and between aP substrate and an N channel, this having a lower concentration andgreater depth than those of the normal P-well.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034]FIG. 1 is a drawing showing the configuration of a firstembodiment of a fingerprint authentication apparatus according to thepresent invention.

[0035]FIG. 2 is a drawing showing the configuration of a secondembodiment of a fingerprint authentication apparatus according to thepresent invention.

[0036]FIG. 3 is a drawing showing the configuration of a thirdembodiment of a fingerprint authentication apparatus according to thepresent invention.

[0037]FIG. 4 is a drawing showing the configuration of a fourthembodiment of a fingerprint authentication apparatus according to thepresent invention.

[0038]FIG. 5 is a schematic representation illustrating judgment of aliving fingerprint and a replica using an optical image sensor in thethird and fourth embodiments of the present invention.

[0039]FIG. 6 is a cross-sectional view showing the structure of imagesensors, (A) showing the structure of an image sensor having no infraredsensitivity, and (B) showing the structure of an image sensor havinginfrared sensitivity.

[0040]FIG. 7 is a circuit diagram showing an element of a generaloptical image sensor.

[0041]FIG. 8 is a flowchart illustrating the first and secondembodiments of a fingerprint authentication apparatus according to thepresent invention.

[0042]FIG. 9 is a flowchart illustrating the third and fourthembodiments of a fingerprint authentication apparatus according to thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] Embodiments of a fingerprint authentication apparatus accordingto the present invention are described in detail below, with referencesmade to relevant accompanying drawings.

[0044] The present invention acquires an image of an object (finger)using an optical image sensor having infrared sensitivity to sense lightscattered or reflected from the object, and in doing so acquires animage (fingerprint pattern) of the object, determines the claritythereof, and performs a judgment as to whether the pattern is livingfingerprint (of a person) or a nonliving fingerprint (replica).

[0045] If the result of this judgment is that the fingerprint is aliving fingerprint, a comparison is made of the obtained pattern with apriorly stored image, and a judgment is made as to whether thefingerprint is that of a particular individual.

[0046] The present invention uses a CCD or a CMOS device as atwo-dimensional optical image sensor having infrared sensitivity, theobject having been imaged by being illuminated with infrared light andan image being obtained therefrom, a clear fingerprint image beingobtained in the case of a living fingerprint, but a clear image notbeing obtained in the case of a replica.

[0047] The present invention is based upon these experimental results.

[0048] In the present invention, Rubber, plastic, or asbestos or thelike are used as replica materials. The reason for using these materialsis that the simplest method of forming a replica of a fingerprint is tofirst make a cast of the finger and then pour the material into thecast, which serves as a mold.

[0049] Although the reason for this phenomenon has not at this point intime been explained at the present time, its repeatability is supportedby experimental results.

[0050] Various embodiments of the present invention are described below.

[0051]FIG. 1 is a drawing showing the configuration of a firstembodiment of a fingerprint authentication apparatus according to thepresent invention.

[0052] This embodiment is an optical fingerprint authenticationapparatus having a prism 18 and a lens 19.

[0053] A feature of this embodiment is the use of an infrared lightsource 12 and an optical image sensor 13 having infrared sensitivity.

[0054] It is worthy to note that the above-noted effect is achievedwithout the use in addition to the optical image sensor 13 of a meansfor identifying a living organism, such as a means for detecting bodytemperature.

[0055] This is possible because this means is integratedly built intothe infrared light source 12 and the optical image sensor 13.

[0056] The optical image sensor 13 with infrared sensitivity will beexplained hereunder.

[0057] Note that it has characteristic in that it responds to infraredlight, producing a clear image in the case of a living organism and annon-clear image in the case of a replica.

[0058] In general, as is widely known, an optical image sensor is formedby a multitude of elements, each formed by a photodiode and anassociated amplifier and being arranged in a matrixed configuration, asshown in FIG. 7.

[0059] More specifically, when light from the light source strikes aphotodiode, the photodiode generates an electrical current proportionalto the incident light. This electrical current is amplified by theamplifier and extracted, resulting in an electrical signal correspondingto the light. To form a matrix of elements configured in this manner,the activated terminals of the amplifiers are connected to thehorizontal lines HL of the matrix, and the outputs of the amplifiers areconnected to the vertical lines VL of the matrix.

[0060]FIG. 6 is a cross-sectional view showing the semiconductor devicestructure in elements of image sensors, FIG. 6(A) showing the structurein an element of an optical image sensor without having infraredsensitivity and FIG. 6(B) showing the structure in the optical imagesensor 13 having infrared sensitivity.

[0061] In an optical image sensor without having infrared sensitivitywhich forming the photodiode between the P-substrate and N-channel N,there is merely a shallow P-well layer, as shown in FIG. 6(A),

[0062] In contrast to the above, in the optical image sensor 13 withhaving infrared sensitivity forming the photodiode, as shown in FIG. 6(B), between the P-substrate and the N-channel N, there is a deepP-well.

[0063] This deep P-well has a lower concentration than that of a usualP-well, and is formed as a deeper layer than that thereof, this beingformed directly below the N-channel.

[0064] As a result, the usual P-well is formed only over the deep P-wellon both sides, and directly below the N-channel layer.

[0065] Because infrared light generates an electrical charge at a deeperlocation in a semiconductor device than visible light, it is possibleusing a deep P-well structure to augment the electrical charge generatedat a deep location.

[0066] Therefore, an optical image sensor 13 having a deep P-wellstructure has sensitivity in the infrared region. In the abovedescription, the example is that of a CCD image sensor.

[0067] A person skilled in the art, however, will understand that thisapplies as well to a CMOS optical image sensor.

[0068] The operation of the first embodiment is described below, withreference made to the flowchart of FIG. 8.

[0069] When performing fingerprint authentication, in response to aninstruction from a host device (not shown in the drawing), a controller11 irradiates the infrared light from the infrared light source 12 tothe prism 18.

[0070] When this is done, the object being authenticated (finger 10 of aliving human, in the normal case) is placed over the prism 18.

[0071] Infrared light incident to the prism 18 is reflected at thesurface at which the finger 10 makes contact with the surface of theprism 18, collected by the lens 19, and input to the optical imagesensor 13. The optical image sensor 13 converts the infrared lightincident thereto to an electrical signal, which is input to the imageprocessing section 14.

[0072] The image processing section 14 performs image processing of thecurrent input from the optical image sensor 13, under the control of thecontroller 11 (step S1 in FIG. 8).

[0073] When this is done, by virtue of the above-described infraredcharacteristics, from the light reflected by the “finger” a clear imageof the finger print is obtained in the case of an actual living finger,but a non-clear image thereof is obtained in the case of a replica of afinger.

[0074] The image processing section 14 detects minutiae from the thusobtained image (step S2 in FIG. 8), and performs a judgment as towhether or not the number thereof is equal to or greater than aprescribed number (FIG. S3 in FIG. 8).

[0075] If the result is that the number of minutiae is less than theprescribed amount, authentication is not possible.

[0076] If, however, the minutiae count is equal to or greater than theprescribed number, the comparison section 15 performs a fingerprintcomparison (step S4 in FIG. 8).

[0077] In performing this fingerprint comparison, a comparison is madebetween image data of the input fingerprint and image data of afingerprint priorly stored in the database 16 and a similaritytherebetween is calculated from the minutiae, this similarity beingexpressed as a value known as the score.

[0078] A judgment is made as to whether or not the score is equal to orgreater than a threshold value (step S5 in FIG. 8).

[0079] If the result of this judgment is that the score is equal to orgreater than the threshold value, a judgment is made that thefingerprint is that of an authorized person, while, if the result ofthis judgment is that the score is less than the threshold value, ajudgment is made that the fingerprint is not that of an authorizedperson.

[0080] Because this embodiment can be easily achieved by replacing thevisible light source of a fingerprint authentication apparatus of thepast with an infrared light source, and replacing the optical imagesensor of a fingerprint authentication apparatus of the past with anoptical image sensor having infrared sensitivity, it is possible toachieve this embodiment as a modification of an existing apparatus.

[0081]FIG. 2 is a drawing showing the configuration of a secondembodiment of a fingerprint authentication apparatus according to thepresent invention. In this fingerprint authentication apparatus, ratherthan using a prism and lens or such optical components, and in contrastto an optical fingerprint authentication apparatus in which a finger isbrought into direct contact with an optical image sensor, an infraredlight source 22 and an optical image sensor 23 having the infraredsensitivity are used, similar to the case of the first embodiment.

[0082] Specifically, in this apparatus, the finger is directlyilluminated, the scattered light therefrom being received by atwo-dimensional image sensor formed by a multitude of light-receivingelements arranged in a two-dimensional pattern.

[0083] When a fingerprint is input, the fingerprint is brought intoproximal contact with a light-receiving surface of the light receivingelements.

[0084] The light-receiving elements having light-receiving surfacesbeing in proximal contact with raised parts of the fingerprint, detectsa bright region to which the scattered light from inside the finger tip,can be reached in a good condition through the raised parts of thefingerprint, as raised parts of the fingerprint.

[0085] In contrast to this, light-receiving elements havinglight-receiving surfaces in proximal contact with valley parts of thefingerprint, detects non-bright region to which the scattered light frominside the finger tip cannot be reached, as valley parts of thefingerprint.

[0086] In FIG. 2, the infrared light source 22 and the optical imagesensor 23 are configured as described above.

[0087] When a fingerprint comparison is being done, the finger 20 isbrought into direct contact with the optical image sensor 23.

[0088] Infrared light illumination from the infrared light source 22 isscattered by the finger 20, this scattered light being received by theoptical image sensor 23.

[0089] Subsequent processing is the same as the processing in the caseof the first embodiment, and the flowchart of FIG. 8 applies in thiscase as well.

[0090] In FIG. 2 and FIG. 1, the lower-order digit of the referencenumerals being the same indicates that these are corresponding elementsof the two embodiments.

[0091]FIG. 3 is a drawing showing the configuration of a fingerprintauthentication apparatus according to the third embodiment.

[0092] In this embodiment, which is a fingerprint authenticationapparatus using a prism 38 and a lens 39, the use of an optical imagesensor 33 having infrared sensitivity is in common with the firstembodiment shown in FIG. 1.

[0093] However, this embodiment uses a combined visible/infrared lightsource 32, in which visible light is mixed with infrared light is used,and consideration is given to the optical image sensor 33, anaccompanying reference processing section 37 is further provided.

[0094] The optical image sensor 33 is formed by a block having infraredsensitivity and a block without having infrared sensitivity.

[0095] Each one of the former and the latter forms the semiconductordevice configurations as shown in FIG. 6(B) and FIG. 6(A), respectively.

[0096] In the case in which the optical image sensor 33 is implementedon a single chip, with this separation into blocks, both blocks resideon one and the same chip.

[0097] Alternately, it is possible to implement the optical image sensor33 with a chip having infrared sensitivity and a chip without havinginfrared sensitivity, this method resulting in an improved chip yield.

[0098] Additionally, an alternative simplified method is that ofpartially affixing a infrared-cutting filter to an optical image sensorhaving infrared sensitivity, thereby forming a block that does not haveinfrared sensitivity in the portion having the infrared-cutting filter.

[0099]FIG. 5 is a drawing illustrating the discrimination between aliving organism and a replica in the optical image sensor 33, the upperpart of which shows the block having infrared sensitivity, and the lowerpart of which shows the block without having infrared sensitivity.

[0100] As shown in FIG. 5(A), in the case in which a finger tofingerprint authenticated is placed on the optical image sensor 33, ifthe finger is an actual living finger, because the image obtained fromthe optical image sensor 33, as shown in FIG. 5(B), because of theinfrared sensitivity as shown in the upper part of the drawing, is aclear fingerprint image, and although the bottom part does not haveinfrared sensitivity, the visible light sensitivity in this regionresults in a clear fingerprint image.

[0101] In the case in which the “finger” was in fact a replica, theimage obtained from the optical image sensor 33, as shown in FIG. 5(C),because of the infrared sensitivity in the upper part of the opticalimage sensor 33, is an unclear fingerprint image, and although there isno infrared sensitivity in the lower part, a clear fingerprint imageresults.

[0102] The reference processing section 37 makes a comparison betweenthe clarity of the input fingerprint images between the block withinfrared sensitivity and the block without having infrared sensitivity.

[0103] As is clear from FIG. 5, in the case of the finger of a livingorganism, there is no difference in clarity between the images obtainedby the two blocks, but in the case of a replica, there is a differencein the clarity between the images obtained by the two blocks. Usingthis, it is possible to distinguish between a living finger and areplica.

[0104] Although for simplicity of description in FIG. 5 the exampleshown is that in which the optical image sensor 33 is divided into twoblocks, it is also possible to divide this optical image sensor 33 intoa greater number of blocks, in which case, the blocks having infraredsensitivity and the blocks not having infrared sensitivity can bedisposed in a checkerboard pattern.

[0105] The finer is the separation into blocks, the closer is the partof the fingerprint image to be compared by the reference processingsection 37, thereby enabling a more precise comparison.

[0106] The ideal arrangement is one in which a block with infraredsensitivity and a block without having infrared sensitivity are disposedfor each line of the optical image sensor 33. Additionally, divisioninto blocks is possible not only in the horizontal direction, as shownin FIG. 5, but also in the vertical direction.

[0107]FIG. 9 is a processing flowchart of processing performed in thesecond embodiment, in which a “Clarity difference within prescribedrange?” step T1 is inserted before the step S1 of FIG. 8. If the resultof the check performed at step T1 is affirmative, the processing ofsteps T2 and thereafter is performed. In FIG. 9, steps T2 through T6correspond to steps S1 to S5 of FIG. 8.

[0108] The following methods can be envisioned as a specific method ofimage comparison between the blocks in the reference processing section37, such a method being performed by, for example, a DSP (digital signalprocessor) within the reference processing section 37.

[0109] The first method is that of performing a Fourier transform of theclarity of each of the blocks with regard to the input fingerprintimage.

[0110] In the Fourier transform in this case, the transition density ofthe bright parts and the dark parts of the fingerprint image isconverted to spatial frequency, the parts having a high transitiondensity having a high spatial frequency, and the parts having a lowtransition density having a low spatial frequency.

[0111] In the case of a living organism fingerprint, because clearimages are obtained from both the block with infrared sensitivity andthe block without having infrared sensitivity, as shown in FIG. 5(B),the spatial frequency for both blocks is high, and there is no differentbetween the spatial frequencies.

[0112] In the case of a replica, however, as shown in FIG. 5(C), becausethe block having infrared sensitivity yields an unclear image, itscorresponding spatial frequency is low, and because image yielded fromthe block without having infrared sensitivity is clear, itscorresponding spatial frequency is high, so that there is a differencebetween the spatial frequencies, this difference enabling elimination ofthe replica.

[0113] A second specific method of image comparison is that in which thestandard deviation of the clarity from each of the blocks with regard tothe input fingerprint image is calculated. In the case of imaging areplica, because the image from the block having infrared sensitivity isunclear, the standard deviation of this clarity is smaller than that ofthe clarity of the image from the block without having infraredsensitivity.

[0114] In the case of a fingerprint from a living organism, there is nodifference between the standard deviation of the blocks.

[0115] In the case of a replica, however, the standard deviation for theblock with infrared sensitivity is low compared with the standarddeviation for the block without having infrared sensitivity, this factbeing used to eliminate a replica.

[0116] A difference in the absolute values of the sensitivity betweenthe block with infrared sensitivity and the block without havinginfrared sensitivity occurs. Because of this, a controller 31 sets theshutter speed for each of the blocks independently, so as to obtainproper images.

[0117] The above-noted shutter speed is the time in a PN junction of theoptical image sensor 33 from the application of a reset to the N-channellayer, which starts the reading of the current signal, until thecompletion of readout, the shutter speed of a block having a highinfrared sensitivity being set so as to be faster than the shutter speedof a block without having infrared sensitivity. As a result, theexposure time of a block with high infrared sensitivity is shorter thanthat of a block without having infrared sensitivity, therebycompensating for the difference in sensitivity, and achieving an overallimage having the same brightness for both blocks.

[0118] The controller 31 can achieve the same effect by appropriatesensor sensitivity settings independently for each block. Specifically,the current amplification factor of an amplifier in the optical imagesensor 33 with respect to a block having infrared sensitivity is setlower than that of an amplifier for a block without having infraredsensitivity.

[0119] Additionally, in the case in which it is difficult for thecontroller 31 to simultaneously set different shutter speeds for twoblocks, as noted above, it is alternatively possible for the controller31 to detect an appropriate shutter speed for each of the blocks and,after imaging at each of the shutter speeds with a time shifttherebetween, to synthesize an image from the images of the individualblocks. This can also be applied in a case in which the amplificationfactors for the two blocks are set differently.

[0120]FIG. 4 is a drawing showing the configuration of an opticalfingerprint authentication apparatus according to the fourth embodimentof the present invention. In this embodiment, rather than using a prismand lens or such optical components, the finger is brought into directcontact with an optical image sensor, the relationship between thisfourth embodiment and the third embodiment being the same as therelationship between the second embodiment and the first embodiment.

[0121] Specifically, in this fingerprint authentication apparatus, acombined infrared/visible light source 42 providing illumination withmixed infrared light and visible light being used and considerationbeing given to the optical image sensor 43, an accompanying referenceprocessing section 47 being further provided.

[0122] The optical image sensor optical image sensor 43 is formed by ablock having infrared sensitivity and a block without having infraredsensitivity. A reference processing section 47 performs a comparison ofthe clarity of the fingerprint images input between the block withinfrared sensitivity and the block without having infrared sensitivitywithin the optical image sensor 43.

[0123] Infrared light illumination from the visible/infrared infraredlight source 42 is scattered by a finger is scattered by a finger 40,and received by the optical image sensor 43. Subsequent processing isthe same as described with regard to the third embodiment, and theflowchart of FIG. 9 applies in this case as well. In FIG. 4 and FIG. 3,the lower-order digit of the reference numerals being the same indicatesthat these are corresponding elements of the two embodiments.

[0124] By adopting the technical constitutions described in detailabove, the present invention achieves a number of effects. The firsteffect is that of, without using the piezoelectric effect and/orpyroelectric effect as in the past to read a fingerprint image, readingthe image with an optical image sensor having infrared sensitivity,resulting in a stable fingerprint authentication apparatus that islittle affected by the ambient temperature.

[0125] The second effect achieved by the present invention is madepossible by performing stable fingerprint authentication with littleinfluence from the ambient temperature, thereby reducing the maintenanceburden in a fingerprint authentication apparatus according to thepresent invention.

What is claimed is:
 1. A fingerprint authentication apparatuscomprising: a imaging section for obtaining an image of an object to befingerprint authenticated, using an optical image sensor having infraredsensitivity; an image processing section, which performs imageprocessing of data obtained from said imaging section and obtaining afingerprint image; and a fingerprint comparison section, which performsa comparison between said fingerprint image and a priorly storedfingerprint image.
 2. A fingerprint authentication apparatus accordingto claim 1, wherein said optical image sensor is selected from a groupconsisting of a CCD image sensor and a CMOS image sensor, each havinginfrared sensitivity.
 3. A fingerprint authentication apparatusaccording to claim 1, further comprising means for shining infraredlight onto an object to be fingerprint authenticated.
 4. A fingerprintauthentication apparatus comprising: an imaging section comprising afirst optical image sensor having infrared sensitivity and a secondoptical image sensor sensitivity in the visible light region, said firstand second optical image sensors being mutually neighboring wherebyobtaining an image of an object to be fingerprint autheticated; an imageprocessing section, which performs image processing of data obtainedfrom said image processing section so as to obtain the fingerprintimage; and a fingerprint comparison section, which performs a comparisonbetween said fingerprint image and a priorly stored fingerprint image.5. A fingerprint authentication apparatus according to claim 4, whereinsaid first and second optical image sensors are both selected from agroup consisting of a CCD image sensor and a CMOS image sensor, a P-welldepth in said first optical image sensor is deeper than that of saidsecond optical image sensor, and a concentration thereof is less thanthat of said second optical image sensor.
 6. A fingerprintauthentication apparatus according to claim 4, wherein said firstoptical image sensors is selected from a group consisting of a CCD imagesensor and a CMOS image sensor each having infrared sensitivity, andwherein said second optical image sensor is formed by providing aninfrared-cutting filter on said first optical image sensor.
 7. Afingerprint authentication apparatus according to claim 4, furthercomprising means for shining infrared light and visible light onto saidobject to be fingerprint authenticated.
 8. A fingerprint authenticationapparatus according to claim 1, wherein a fingerprint image is obtainedwith said object to be fingerprint authenticated brought into contactwith said imaging section.
 9. A fingerprint authentication apparatusaccording to claim 4, wherein a fingerprint image is obtained with saidobject to be fingerprint authenticated brought into contact with saidimaging section.
 10. A fingerprint authentication apparatus according toclaim 1, wherein a fingerprint image is obtained with said object not incontact with said imaging section.
 11. A fingerprint authenticationapparatus according to claim 4, wherein a fingerprint image is obtainedwith said object not in contact with said imaging section.